Development accelerators



United States Patent 3,307,948 DEVELOPMENT ACCELERATORS Robrecht Julius Thiers, Brasschaat, Jozef Frans Willems, Wilrijk-Antwerp, and Raymond Leopold Florens, Edegern, Belgium, assignors to Gevaert Photo-Producten N.V., Mortsel, Belgium, 21 company of Belgium No Drawing. Filed May 24, 1965, Ser. No. 458,489

Claims priority, application Belgium, June 2, 1964,

43,694, Patent 648,710 11 Claims. (Cl. 96-663,)

This invention relates to a process for improving the quality of photographic material, more particularly of silver halide emulsion layers the developability and the general light-sensitivity of which are increased.

It is known that the general sensitivity of photographic emulsions which can already optimally be sensitized for the whole range of the spectrum by means of chemical sensitizers such as sulphur sensitizers, can still further be increased by the addition of polyoxyalkylene glycols to these emulsions (cf. US. patent specifications 2,240,472 and 2,423,549).

It is also known that the general sensitivity of a photographic silver halide emulsion layer can be enhanced by the incorporation of alkylene oxide polymers into the photographic material. These polymers are obtained by polymerization of alkylene oxide in the presence of dehydrating products of hexitol ring compounds or aliphatic alcohols (cf. U.S. patent specifications 2,400,532 and 2,716,062) or in the presence of aliphatic acids, amines, amides or phenols (cf. U.S. patent specification 2,716,- 062).

It is further known that these alkylene oxide polymers should possess a molecular weight of at least 1500 to 2000 for obtaining an appreciable increase of the sensitivity.

Contrary to the other known methods for increasing the sensitivity of a silver halide emulsion wherein chemical sensitizers enhance the inherent sensitivity and cyanine dyestuifs enhance the spectral sensitivity, it appears that the increase in sensitivity of the silver halide emulsions containing the above-mentioned alkylene oxide polymers is due to the compounds activation of the development of these silver halide layers by means of said polymers. Therefore, these compounds can be considered as development activators or accelerators.

It is, however, also known that polyoxyalkylene glycols, besides the advantage of development activation when incorporated into a photographic silver halide emulsion, especially at high temperatures and rather strong relative humidity, cause a considerable increase of the fog formation.

These drawbacks are avoided by using polyoxyalkylene derivatives described in our U.S. patent specification 3,158,484 filed October 24, 1961, and prepared by condensation of polyoxyalkylene glycols, which are themselves of too low molecular weight for development acceleration, with an aliphatic aldehyde, a dicarboxylic acid, a dicarboxylic anhydride or a diisocyanate.

It has now been found that the development of a photographic material containing light-sensitive silver halides is advantageously activated by using a ter-condensation product of a dialkanolamine and/ or a dialkanolamide with a diisocyanate and a polyoxyalkylene glycol.

In case these condensation products are incorporated into a light-sensitive silver halide emulsion layer, their sensitivity is increased to a relatively considerable extent, the fog formation, however, in only a very small measure.

ICC

The structural units of these ter-condensation products can be represented by the following formula:

wherein:

R represents an alkyl radical, preferably a higher alkyl radical, such as a straight-chained alk-yl radical with 10 to 18 carbon atoms or a R CO radical, wherein R, has the same significance as R R represents a lower alkyleneoxyradical such as ethyleneoxy, a propyleneoxy, an isopropyleneoxy or an isobutyleneoxy radical,

x and y each represents an integer from 1 to 50,

R represents an ethyleneoxy radical or a chain of ethyleneoxyand isopropyleneoxy radicals, and

A represents a bivalent organic radical, e.g., a bivalent aliphatic, cycloaliphatic or aromatic radical or an alkylene-substituted monovalent aromatic radical, e.g.,

The most appropriate condensation products are those prepared by starting from dialkanolamines and/or dialkanolamides, which contain an aliphatic hydrocarbon chain with 12 to 18 carbon atoms to which is attributed the strong surface active character of these products. Hereinafter follow some examples of appropriate dialkanolamides:

wherein coco means the alkyl radicals of the fatty acid mixture from coconut oil.

tall- C O N wherein tall means the alkyl radicals from the fatty acid mixture from tall oil.

As diisocyanates are considered aliphatic diisocyanates, such as hexamethylene diisocyanate, as well as aromatic diisocyanates, such as toluene diisocyanate.

As polyoxyalkylene glycols are especially considered polyoxyethylene glycols. Also mixed polyoxyalkylene glycols, partlycomposed of oxyethylene units and partly of oxyisopropylene units can be used in the condensation, but the ratio of both should be chosen in such a way that finally Water-soluble products are formed. The average molecular weight of the polyoxyalkylene glycols used in the condensation lies preferably between 300 and 2000.

Themolar ratio of the reaction components is preferably chosen in such a way that at least as much diisocyanate as dialkanolamine or dialkanolamide is caused to react with a sufficient amount of polyoxyalkylene glycol that water-soluble reaction products are formed. In this connection it is to be noted that the condensation products of dialkanolamines or dialkanolarnides with dissocyanates are not water-soluble.

The preferred molar ratio of the reaction components is of 2 mol of diisocyanate, 1 mol of dialkanolamine or dialkanolamide and 1 mol of polyoxyalkylene glycol.

Preferably, the condensation is carried out in an inert solvent wherein the reaction components dissolve, e.g., dioxane or benzene. I

Several methods can be applied for the condensation. Thus, a dialkanolamine and/ or dialkanolamide can first be precondensed at low temperature with a diisocyanate in a solvent, and then the condensation product formed can further be condensed by boiling under reflux with a polyoxyalkylene glycol. The reversed processing step, however, is also possible and even more appropriate in certain cases for obtaining water-soluble products.

The condensation products are isolated in the usual way from the reaction medium by evaporation of the solvent or by precipitation into a liquid miscible with the solvent, in which liquid, however, the condensation product is not soluble. An appropriate precipitating means is for instance diethyl ether.

As an illustration follows hereinafter a detailed description of the preparation of a condensation product, which is used according tothe invention as development 4 accelerator. Products mentioned in the table are analogously prepared.

PREPARATION OF A CONDENSATION PRODUCT NO. 1

700 g. (0.35 mol) of polyglycol (average molecular weight 2000) in 1100 ccs. of anhydrous dioxane are brought into a 5 liter flask equipped with a stirrer, a reflux condenser provided with a calcium chloride tube, a thermometer and a dropping funnel. This dissolution of the polyglycol is accelerated by a slight heating. To the solution cooled at 20 C. is added within approximately 5 min. a solution of 121.7 g. (0.7 mol) of toluene-2,4- diisocyanate in 100 cos. of anhydrous dioxane whilst stirring. The reaction is slightly exothermic and the temperature of the reaction mixture is kept between 20 and 25 C. by cooling the flask with ice.

After adding the diisocyanate, the reaction mixture is further stirred for another 20 min. and a solution of 100.5 g. (0.35 mol) of lauroyldiethanolamide (melting point: 4344 C.) in 400 ccs. of anhydrous dioxone is added within 5 min. (the laurydliethanolarnide is obtained by reaction of H C-(CH -COCl with diethanolamine). By cooling with ice-water, the temperature of the reaction mixture is maintained between 20 and 25 C. After adding the amide, the reaction mixture is further stirred for another 20 min. at 20-25 C., heated to boiling point and refluxed for 4 hrs. After cooling down to room temperature again, 3.52 liters of anhydrous ether cooled to 5 C. are dropwise added. The result is a white amorphous precipitate, which is filtered off and washed with anhydrous ether. The product obtained is fully watersol-uble. Yield: 790 g. (86%).

Further examples are given hereinafter in the form of a table. The molar ratio of the reaction compounds amounts to 1/2/1 in all of the examples.

' N01. 01' tthe A. Dialkanolamide or dialkanolcont ensa ion amine u T product B Dnsocy mate 0. P013 g1 col CHzCIIzOII 2 C11II;3 -C ON O=C:N(CI I )GN=O:O Polyethylene glycol,

a era e In 1. CHzCHzOH V g 0 eight 3 Idem. Idem. Polyethylene glycol,

average mol. weight 1,000

4 Idem. Idem. Polyethylene glycol,

. aygrage mol. weight 5 Idem. Idem. Polyethylene glycol,

average mol. weight 2,060.

6 Idem. Idem. Polyethylene glycol,

average mol. weight 300. 021140) XII 7 coco-C ON Idem. Polyethylene glcycol, (Cm-Wyn average mol. Weight z+y=5 CiILO) xII 8 tall-C ON Idem. Do.

(C 2H4O 3-H I-l-y= N C O CzHsOH l 9 C11H,3C ON 0 CN- CH3 Polyethylene glycol,

f: ra CiHiOH ifh 10 Idem. Idem. Polyethylene glycol, average mol. weight 2,000

No. of the A. Dialkanolamide or dialkanolcondensation amine B. Diisoeyanate C. Polyglyeol product 11 coco-N O=CN(CH2)GNC=O Polyethylene glycol,

average mol. weight (C2H40)y 1 1,000.

rr+y= 5 (CqHiO) xH l2 Ci7H31C ON Idem. D0.

( CzI-LO) H CHCH2OH 13 C17Hai-C 0-N Idem. D0.

CH-CH: 0 H

14 Idem. Idem. Polyethylene glycol,

aver-age mol. weight 2,000.

N C 0' CgHlO H l 15 CwHm-C O-N O ON- CH3 D0.

2110) H 16 coco-N Idem. Polyethylene glycol,

. average mol. weight (C2H-10) I-I The condensation products can be added to the coating composition of a silver halide emulsion and/or incorporated into a water-permeable layer, which applied under or over the emulsion layer forms a water-permeable system with the silver halide emulsion layer and thus can come into effective contact with the silver halide.

The condensation products can be incorporated into the coated emulsion layer either by treating the emulsion layer with an aqueous solution of these condensation products or by coating this layer with a water-permeable layer, which contains the condensation products, or also by bringing the condensation products from a water-permeable layer lying under the emulsion layer, wherein the said condensation products are present, into effective contact with the silver halide.

The water-soluble condensation products can be added to the light-sensitive silver halide emulsion during different preparation steps of the light-sensitive material: for instance they can be incorporated as separate addition either mixed with one or more ingredients, which are used in the preparation of the silver halide grains during the physical or chemical ripening process, or an other moment preceding the application of the emulsion.

The development accelerators are preferably added to the silver halide emulsion composition after the chemical ripening process and just before applying the emul- SlOIl.

The condensation products are preferably added in dissolved form in water or in an aqueous mixture of water and water-miscible organic solvents that do not impair the photographic properties of the light-sensitive silver halide emulsion.

The optimum amount of development accelerator added to the silver halide emulsion depends on the chosen compound itself, on the kind of the colloid binding agent for the silver halide grains and on the amount and the kind of the silver halide in the emulsion. In general, however, the above-mentioned condensation products are added to the light-sensitive material in amounts from mg. to 10 g. per mol of silver halide. In the developing bath they are normally used in amounts ranging from 0.1 g. to 10 g. per liter. If necessary, these compounds can also be added in amounts which exceed these limits.

The step of increasing the sensitivity according to the present invention can be combined with a method known as chemical sensitization, whereby together with the mentioned condensation products usual amounts of chemical sensitizers are added to the silver halide emulsion, e.g., sulphur-containing compounds such as allyl isothiocyanate, allylthiourea or sodium thiosulphate, reducing compounds such as the tin compounds described in our Belgian patent specifications 493,464 filed January 24, 1950 and 568,687 filed June 18, 1958, the iminoaminomethanesulphinic acid compounds described in our German patent specification 1,020,868 filed March 25, 1958,, or noble metal compounds such as gold, platinum, palladium, iridium, ruthenium and rhodium compounds. As a matter of fact, the sensitizing action of condensation products used in the present invention comes in addition to the sensitizing action of the sensitizing compounds originally present in gelatin.

The development-accelerating compounds applied in the present invention can also be used in combination with stabilizers and fog-inhibiting compounds for the silver halide emulsion, for instance with mercury compounds or organic sulphur-containing compounds that form an insoluble silver salt with silver ions, preferably heterocyclic nitrogen-containing thione compounds such as benzothiazolin 2 thione and l-phenyltetrazolin-S- thione, the compounds described in our Belgian patent specifications 571,916 filed October 10, 1958 and 571,917 filed October 10, 8 and compounds of the oxytriazolopyrimidine type, e.g. 5-methyl-7-hydroxy-s-triazolo[1,5-a] pyrimidine. Further is also mentioned the combination with sensitizing and stabilizing cadmium salts in the lightsensitive material as well as in the developing bath.

Other developmeut-accelerating compounds such as organic onium compounds and polyonium compounds, preferably of the ammonium or sul-phonium type, e.g., quaternary tetraalkylam-monium salts, alkylpyridinium salts, bis-alkylenepyridinium salts, alkylquinolinine salts and trialkylsulphonium salts can be applied together with the development accelerators used according to the invention and this in the developing solution as well as in the light-sensitive material. Other ingredients, such as colour couplers, developing substances, hardening agents and wetting agents, can moreover be added to the emulsions in the ordinary way.

The development of low sensitive as well as of high sensitive, of fine-grained as well as of coarse-grained silver halide emulsions is accelerated by the condensation products mentioned. These products are considered for the development acceleration of X-ray emulsions as well as of the most different spectrally or non-spectrally sensitized emulsions. Thus, they can be incorporated into the photographic emulsion either with or without optical sensitizers and can be used for increasing the sensitivity of negative emulsions as well as of positive emulsions.

The following examples illustrate the invention.

Example 1 A washed negative gelatino-silver bromo-iodide emulsion (average grain size of the silver halide: 0.8 the silver halide of which consists of 94.5 mol percent of silver bromide and 5.5 mol percent of silver iodide is ripened at 45 C. The emulsion ready for coating contains per kg. 50 g. of silver halide, 75 g. of gelatin, 30 mg. of optical sensitizer with the following structural formula:

C2H5 02H:

50 mg. of 5-methyl-7-hydroxy-s-triazolo[1,5-a]pyrimidine as stabilizer and 500 mg. of saponine as wetting agent.

This emulsion is applied to a cellulose triacetate support and dried (test strip 1). Other test strips are prepared by adding each time to 1 kg. of the above emulsion before coating, the amounts of development accelerators listed below. All test strips are then exposed in the same conditions through a grey wedge and developed for 7 min. at 20 C. in a bath of the following composition:

Water c.c.s 800 Monomethyl-p-aminophenol sulfate g 2 Hydroquinone g 5 Anhydrous sodium sulfite g 100 Borax g Boric acid g 5 Potassium bromide g 0.5

Water up to 1000 c.c.s.

SENSITOMETRIG RESULTS Test N0. of the Amount Relative strip condensation by weight sensitivity G arnrna Fog product added, g.

100 0. 41 0. 06 2 1 186 0. 45 0. 0s 8 1 141 0. 45 0. 07 10 1 182 0. 45 0. 0s 13 1 200 0. 46 0. 06 14 1 214 0. 45 0. 08 15 1 182 0. 4s 0. 0s 1 1 159 0. 0. 08 3 0. 5 141 0. 45 0. 03 5 0. 5 170 0. 0. 08

Example 2 A washed coarse-grained gelatino-silver bromo-iodide emulsion (average grain size: 1.2 composed of 98.2

mol percent of silver bromide and 1.8 mol percent of silver iodide is ripened at 42 C.

The emulsion contains per kg. g. of silver halide, 70 g. of gelatin, 50 mg. of 5-methyl-7-hydroxy-s-triaz01o-[1, 5-a]pyrimidine as stabilizer and 500 mg. saponine as wetting agent.

This emulsion is applied to a cellulose triacetate support and dried (test strip 1). Other test strips are prepared by adding each time to 1 kg. of the above emulsion before coating 1.5 g. of the development accelerators listed below. All of the test strips are then exposed in the same conditions through a grey wedge and developed for 5 min. at 20 C. in the development composition from Exmaple 1.

SENSI'IOMETRIO RESULTS No. of the Relative Test sti 1p condensation sensitivity Gamma Fog product 0. 44 0.01 2 162 0. 62 0. 01 8 152 0. 60 0.01 10 174 0. 65 0.01 13 152 0. 65 0. 01 14 174 0. 60 0. 02 15 162 O. 65 0. 01 1 174 0. 60 0. 01 5 0. 63 0. Ol 7 162 0. 54 0. 01

Example 3 Five identical test strips (ae) of a photographic material, prepared as in Example 1 but without development accelerators, are exposed in the same way through a grey wedge. The test strips are developed for 6 min. at 20 C.

Test strip a is developed in a developing bath as described in Example 1. Each of the remaining test strips b-e is developed in a separate developing bath as described in Example 1, to which bath, however, 3 g. of the development accelerator as given in the table were added per liter.

SENSITOMETRIC RESULTS No. of the Relative Test strip condensation sensitivity Gamma Fog product Example 4 A silver halide emulsion ready for coating, prepared as described in Example 1 is divided into 3 equal parts. To one of these parts no development accelerator is added (test material 1). To the remaining parts are added 1 g. of polyoxyethylene glycol, having an average molecular weight of 6000 (test material 2), and 1 g. of condensation product No. 10 (test material 3) respectively.

The three silver halide emulsions are each applied in the same way to a separate cellulose triacetate support. After storing for 36 hrs. at 57 C. in a medium of 34% of relative humidity, the obtained test materials are exposed and developed for 10 minutes as described in Example 1.

The sensitometric results are given in the table below.

We claim:

1. Process for developing photographic materials containing light-sensitive silver halide which comprises the step of developing said materials in the presence of a photographic developing agent and of a water-soluble compound formed by condensation of at least one member selected from a dialkanolamine and a dialkanolamide with an organic diisocyanate and a polyoxyalkylene glycol the amount of organic diisocyanate to said member being in the range of a molar ratio of 12:1 and the amount of said glycol being sufiicient to impart water solubility to the ultimate condensation product.

2. Photographic light-sensitive element comprising a silver halide emulsion layer incorporating a water-soluble compound formed by condensation of at least one member selected from a dialkanolamine and a dialkanol-amide with an organic diisocyanate and a polyoxyalkylene glycol the amount of organic diisocyanate to said member being in the range of a molar ratio of 1-2z1 and the amount of said glycol being sufficient to impart Water solubility to the ultimate condensation product.

3. Photographic developing bath comprising a silver halide photographic developing agent and in dissolved state a compound formed by condensation of at least one member selected from a dialkanolamine and a dialkanolamide with an organic diisocyanate and a polyoxyalkylene glycol the amount of organic diisocyanate to said member being in the range of a molar ratio of 12:1 and the amount of said glycol being suflicient to impart Water solubility to the ultimate condensation product.

4. Photographic light-sensitive element comprising a silver halide emulsion layer incorporating a water-soluble condensation product containing recurring units of the formula:

wherein 5. Photographic developing bath comprising a silver halide photographic developing agent and in dissolved state a condensation product containing recurring units of the formula:

R is an alkyl or acyl radical,

R is a lower alkyleneoxy radical,

x and y each is an integer from 1 to 50,

R is a member selected from an ethyleneoxy radical and 10 a chain of ethyleneoxy and isopropyleneoxy radicals, and A is a bivalent organic radical.

6. Photographic light-sensitive element comprising a silver halide emulsion layer incorporating a water-soluble condensation product formed by reaction of 1 mol of a member selected from dialkanolamine and dialkanolamide with 2 moles of organic diisocyanate and 1 mol of polyoxyalkylene glycol. I

7. Photographic developing bath comprising a silver halide photographic developing agent and in dissolved state a water-soluble condensation product formed by reaction of 1 mol of a member selected from dialkanolamine and dialkanolamide with 2 moles of organic diisocyanate and 1 mol of polyoxyalkylene glycol.

8. Photographic light-sensitive element comprising a silver halide emulsion layer incorporating a water-soluble compound formed by condensation of at least one member selected from a dialkanolamine and a dialkanolamide with an organic diisocyanate and a polyoxalkylene glycol having an average molecular weight of 300 to 2000 the amount of organic diisocyanate to said member being in the range of a molar ratio of l2:1 and the amount of said glycol being sufficient to impart water solubility to the ultimate condensation product.

9. Photographic developing bath comprising a silver halide photographic developing agent and in dissolved state a Water-soluble compound formed by condensation of at least one member selected from a dialkanolamine and a dialkanolamide with an organic diisocyanate and a polyoxyalkylene glycol having an average molecular weight of 300 to 2000 the amount of organic diisocyanate to said member being in the range of a molar ratio of l2:1 and the amount of said glycol being sufficient to impart water solubility to the ultimate condensation product.

10. Photographic light-sensitive element comprising a silver halide emulsion layer incorporating per mol of silver halide mg. to 10 g. of water-soluble compound formed by condensation of at least one member selected from a dialkanolamine and a dialkanolamide with an organic diisocyanate and a polyoxyalkylene glycol the amount of organic diisocyanate to said member being in the range of a molar ratio of l-2z1 and the amount of said glycol being suflicient to impart water solubility to the ultimate condensation product.

11. Photographic developing bath comprising a silver halide photographic developing agent and in dissolved state and per liter 0.1 g. to 10 g. of a compound formed by condensation of at least one member selected from a dialkanolamine and a dialkanolamide with an organic diisocyanate and a polyoxyalkylene glycol the amount of organic diisocyanate to said member being in the range of a molar ratio of 12:1 and the amount of said glycol being suificient to impart water solubility to the ultimate condensation product.

No references cited.

J. TRAVIS BROWN, Acting Primary Examiner. Q DAVI 4 WI FE flr= 

1. PROCESS FOR DEVELOPING PHOTOGRAPHIC MATERIALS CONTAINING LIGHT-SENSITIVE SILVER HALIDE WHICH COMPRISES THE STEP OF DEVELOPING SAID MATERIALS IN THE PRESENCE OF A PHOTOGRAPHIC DEVELOPING AGENT AND OF A WATER-SOLUBLE COMPOUND FORMED BY CONDENSATION OF AT LEAST ONE MEMBER SELECTED FROM A DIALKANOLAMINE AND A DIALKANOLAMIDE WITH AN ORGANIC DIISOCYANATE AND A POLYOXYALKYLENE GLYCOL THE AMOUNT OF ORGANIC DIISOCYANATE TO SAID MEMBER BEING IN THE RANGE OF A MOLAR RATIO OF 1-2:1 AND THE AMOUNT OF SAID GLYCOL BEING SUFFICIENT TO IMPART WATER SOLUBILITY TO THE ULTIMATE CONDENSATION PRODUCT. 